A seven day continuous intravenous infusion of cytosine arabinoside in association with a three day schedule of intermittent daily doses of daunorubicin has been shown to be highly effective chemotherapy for the induction of remission in adults with acute nonlymphocyte leukemia. A complete remission rate of 60% is obtained with this combination. Addition of levamisole to this induction regimen dose not enhance this response rate. Serum muramidase levels appear to accurately reflect disease activity in a large proportion of patients with acute non-lymphocytic leukemia. Carcinoembryonic antigen and serum immunoglobulin concentrations do not appear to accurately reflect disease activity. Similarly, biochemical testing of leukemic bone marrow cells does not allow for selection of favorable groups of patients to be treated with cytosine arabinoside (kinase-deaminase ratio) or daunorubicin alone (daunorubicin reductase level). Reverse transcriptase has been identified in the bone marrow cells of leukemia patients prior to treatment and in morphologically normal peripheral cells during complete remission. One interpretation of this data is that morphologically and functionally normal granulocytes in the peripheral blood of leukemia patients in complete remission may be derived from leukemic cells.